Opthalmological microscopes as such are known. They comprise a main objective, a magnification system disposed thereafter, i.e. behind the main objective, and a binocular system with oculars (eyepieces). In order to provide a stereoscopic microscope in a magnification system, which is, for example, designed as a zoom system, the main beam path, which passes the main objective lens may be split into a number of beam paths. Further, opthalmological microscopes are known, which allow for a simultaneous inspection of the object by a first user (main surgeon) and a second user (assistant).
Intraocular surgery requires supplementary optical systems, for example in order to microscopically inspect the fundus or parts of the vitreous body of a human eye, which are close to the fundus. These consist of lenses, which are disposed in front of the main objective at the side of the object.
A supplementary optical system of this kind is described in the brochure “SDI II, BIOM II” of Oculus Optikgeräte GmbH published in 1998, as well as in U.S. Pat. No. 4,856,872. This supplementary optical system comprises a lens (opthalmoscopical lens) to be positioned close to the object to be inspected, and a lens (reduction lens), which is positioned closer to the main objective.
From DE 41 14 646 C2 a solution is known, according to which an ophtalmological attachment for a surgical microscope is accommodated in an attachment housing, which is laterally positionable with respect to the main objective. The attachment comprises an ophtalmoscopical lens, an optical image erecting system and a slideable lens (correcting lens) for focussing.
The image erecting system is needed, because the supplementary optical systems reverse the microscopic image with respect to its height extension and its lateral extension, thereby giving a pseudo-stereoscopic virtual image. This means among other things that the front and the back of depth perception of the intermediate image created by the ophtalmoscopical lens are reversed. However, in order to allow for microsurgical operations, an erected, stereoscopically correct image is required. For this reason, in order to avoid the otherwise resulting pseudo-stereoscopic effect in viewing, a reversal (an exchange) of the two viewing beam paths (reversal of pupils) must occur simultaneously to the required erection of the image. An especially preferred embodiment of such an optical system for erecting images is known as SDI-System (stereoscopic diagonal inverter). A system of this kind is known, for example, from the already mentioned brochure “SDI II, BIOM II” dating from 1998. However, the use of such SDI systems is accompanied by considerable disadvantages for the microscope system or the image quality of the microscope. In particular, adapting the optical beam path of these supplementary systems to that of the stereo microscope has proved to be very cumbersome. Frequently, this results in poor image quality and field clipping, which is caused by insufficient mechanical adaptation of the SDI-system to the microscope. Further, the overall height of such SDI-systems influences the ergonomic overall height of the microscope in a negative way.